MAKING
1) Into a very large bowl, place the sliced aubergines along with the walnuts.
2) To this, add 2 pints of cold water.
3) On high power, cook covered for 12 to 14 minutes, or until it starts boiling.
4) Drain thoroughly and again bring the aubergines to a boil, in 1 pint of cold water. Drain thoroughly. Keep aside.
5) Into a small bowl, put the walnut and sunflower oils.
6) To this, add the flour and milk and combine well.
7) On high power, cook for 2 minutes.
8) Then, beat with a whisk and cook again for 1 to 2 minutes, or until the mix thickens around the edge.
9) Beat again and then add salt and pepper to taste.
10) To the sauce, add the grated Cheddar and 1 tablespoon of Parmesan cheese. Mix well.
11) Into the bottom of a 2-pint flameproof dish, put a layer of the aubergine and nut mixture.
12) On top, add half the tomatoes, half the oregano and half the sauce.
13) Continue to layer the remaining mixture in the same way and finish with the sauce.
14) On Defrost/Low setting, cook for 15 minutes, giving the dish a half-turn halfway through cooking. Cook until the aubergine is tender.
15) To prepare the topping, combine the breadcrumbs and Parmesan cheese.
16) Over the sauce, add the topping and with a non-stick vegetable parchment, cover well.
17) On high power, cook for 4 to 5 minutes.
18) Now, remove the cover and brown under the grill, if desired.

SERVING
19) Serve the Walnut and Aubergine Gratin immediately, along with crusty bread.